1. Field of the Invention
This invention relates to a process for preparing liquefied proteins having a high nutritive value and being free of fish smell and bitterness from bodies of fishes captured in large quantities such as a saurel, sardine, mackerel pike, walleye pollack, Atka mackerel and krill. More specifically, the invention relates to a process for the production of fish meat extracts which comprises charging large quantities of fish bodies directly in a reaction vessel without conducting a pre-treatment of finely cutting them mechanically, and liquefying them with proteinases twice at a pH of 9.0 to 10.0 and at a pH of 5.0 to 6.0, to thereby obtain liquefied proteins having a high nutritive value (such as proteose, polypeptide and peptide), low temperature-treated fish oils of a low acid value and bone dust meals.
2. Description of the Prior Art
According to the conventional process for the preparation of liquefied proteins (fish meat extracts), liquefied proteins are generally prepared by removing the internals from starting fishes, conducting a pretreatment (primary treatment) of cutting and grinding heads, bones, muscles and the like by a cutter, a meat grinder or the like to form a slurry, which requires great labor power, and decomposing and liquefying the slurry with a proteinase at a pH approximating 7.0 (under neutral conditions). In this conventional process, during the cutting step, autolysis enzymes in fish bodies are activated to promote oxidation and hydrolysis on contact with ambient air, and the decomposition is further accelerated by a proteinase added to the fish meat slurry, whereby proteins are converted to free amino acids of a bitter taste and fats are decomposed to low-molecular-weight fatty acids having a strong smell. Accordingly, the so obtained liquid layer portion is not edible at all because of a putrid smell and a strong bitterness. Further, the above-mentioned cutting or grinding pre-treatment requires great labor power.